Formic acid systematically called methanoic acid. It is an important intermediate in chemical synthesis and occurs naturally, most famously in the venom of bee and ant stings. It is mixed with water and most polar organic solvents. Liquid and solid formic acid consists of an effectively infinite network of hydrogen-bonded formic acid molecules.

A significant amount of formic acid is produced as a byproduct in the manufacture of other chemicals, especially acetic acid. This production is insufficient to meet the present demand for formic acid, and some formic acid must be produced for its own sake.

A colorless caustic fuming liquid, HCOOH, used in dyeing and finishing textiles and paper and in the manufacture of fumigants, insecticides, and refrigerants. Some insects especially red ants in their bite or sting secrete formic acid. It has many industrial uses, in textile and leather manufacture, as an industrial solvent, and as an intermediate.